If you wish to influence the precise source or quality of materials, you can tell the vendor from whom you want to procure a material which manufacturer the material is to be supplied by and the part number used by that manufacturer.
You can also tell your vendor exactly which of a manufacturer’s plants is to supply the material you wish to procure.
The manufacturer’s part number (MPN) and description, as well as the specific manufacturing plant (if applicable), are included in the data sent to the vendor with the purchase order.